Variable mixture carburetor



Feb. 1, 1966 M. J. REEVES VARIABLE MIXTURE CARBURETOR 5 Sheets-Sheet l Filed May 28, 1962 WR m1 M w. M M

Feb. 1, 1966 M. J. REEVES VARIABLE M IXTURE CARBURETOR Filed May 28, 1962 5 Sheets-Sheet 2 INVENTOR. MLCLM J'. '7551/55 BY 74550; Arr-@AMEV Feb. 1, 1966 M. J. REEVES 3,232,588

VARIABLE MIXTURE CARBURETOR Filed May 28, 1962 5 Sheets-Sheet 3 ATTORNEY United. States Patent C) 3,232,588 VARIABLE MIXTURE CARBURETOR Malcolm J. Reeves, R0. Box 292, Shoshoni, Wyo. Filed May 28, 1962, Ser. No. 198,370 7 Claims. (Cl. 261-50) The present invention relates to carburetors for internal combustion engines and more specifically to an improved construction for regulating and controlling the fuel-air ratio being delivered to an engine, independently of the throttle.

Separate mixture controls for carburetors have been known to the prior art, but for the most part such devices have been employed exclusively in the aircraft industry where langer and more expensive installations are tolerated. Several attempts have been made to regulate the fuel-air mixture in less expensive carburetors, such as the type employed on automobiles; however, little success has been achieved in this direction.

It is, therefore, an object of the present invention to provide a simplified carburetor which will enable the operator of a vehicle, particularly an automobile, to easily regulate the fuel-air ratio being fed to the vehicle engine so as to achieve maximum economy of operation.

Another object of the invention is to combine a simple and effective fuel shut-off capability with the mixture control mechanism in a carburetor.

Other objects and advantages of the present invention will become apparent upon a reading of the following specification taken in conjunction with the accompanying drawings in which:

FIGURE l is an end elevational view of the carburetor of the present invention.

FIGURE 2 is a fragmentary cross-sectional side elevational view of the carburetor taken along lines 2 2 in FIGURE l.

FIGURE 3 is a cross-sectional end elevational view taken along lines 3 3 in FIGURE 2.

FIGURE 4 is an elevational View taken along lines 4 4 in FIGURE 2 with a portion of the fuel connector valve broken away and shown in cross-section.

FIGURE 5 is an enlarged perspective view of the fuel vaporizer bar.

FIGURE 6 is an enlarged perspective view of the fuel and air valve controls operated by the throttle and mixture control shafts.

FIGURE 7 is an end elevational view taken along lines 7 7 in FIGURE 2, which line is coincident with the joint between the two portions of the fuel bowl casting.

FIGURE 8 is a graph showing fuel iiow plotted on the ordinate and throttle position plotted on the abscissa.

FIGURE 9 is a double graph illustrating in solid lines the relationship between fuel ow, plotted on the ordinate, and throttle position, plotted on the abscissa, with varying settings of the mixture control shaft. The relationship between fuel-air ratio and throttle position is shown in dash lines.

FIGURE l0 is a graph showing the relationship between fuel-air ratio, plotted on the ordinate, and mixture control position plotted on the abscissa, with three different throttle settings as parameters.

In general, the inventive features of the present invention center around the functioning of a reciprocably movable needle and associated valve assembly which meters a quantity of fuel to a plurality of open ports through which the fuel passes to charge the air flowing past the ports. Ordinarily, the venturi effect of a constricted carburetor throat produces increased fuel flow 3,232,588 Patented F eb. I, 1966 ICC through the fuel jets because of the ever diminishing pressure in the vicinity of the throat and jets as the passing air velocity increases. Although such a throat could be employed in the present invention, the preferred embodiment thereof makes use of a simplified rectangular air passage having straight sides. The velocity of the air flowing past the fuel ports produces a sucient pressure differential between the ports and the carburetor fuel bowl to produce a flow of fuel from the fuel bowl. The quantity o-f fuel is controlled precisely by the mechanism substantially comprising the invention.

Briefly, two variable controls, throttle and mixture, provide regulation of the fuel-air ratio over the entire ran-ge of engine operation. Both of these controls are linked to the reciprocable needle of the fuel metering means, providing independent control thereof by either. A third device incorporated within the inventive structure makes possible the selection of either of two limiting minimum conditions when the throttle is closed, that is, idle fuel ow or complete fuel shut off.

In `addition to its direct linkage to the fuel flow control, the throttle also actuates a pair of co-planar air valves which control the air flow into the engine intake manifold. By vcoordinated operation of the available controls and adjustments, a highly elli-cient operation can be maintained throughout the range off engine performance and operating conditions as will more fully appear in the following detailed description of an exemplary embodiment of the invention.

Referring now to the drawings for a detailed description of the canburetor of the present invention, and in particular :to FIGURES 2 andy 3, for this purpose, it will be seen that the carburetor generally indicated as 2, includes a fuel bowl 5, including a float 4, and an air passage 10 separated from the bowl lby a wall partition 12 and otherwise defined by the top, bottom, and sides of the canbnretor housing, generally designated at I4. Through appropriate metering devices, to Ibe later explained, a quantity of volatile fuel, such as gasoline, is delivered from a fuel reservoir in the fuel bowl 5 to charge the incoming air in the air passage di?. The charged air is then admitted to the cylinders of an internal combustion engine, where its stored energy is removed to produce power output, as is well known in 'the art.

Fuel -is charged into the incoming air through a plurality of open ports 21 in a vaporizing lbar 25 situated centrally and rigidly xed within the air passage 10. From the metering device in the fuel bowl, fuel is conducted through an external conduit 27 and a threaded bushing 29, which passes through the wall of the air passage ill?, into a -bore 3'1 in the vaporizing -bar 25 which interconnects the fuel ports 21. A pair of vertical holes 26 in the bar 25 establish an air vent for the fuel passa-ge 31. By principles well known to the art, moving air which passes the open ports 21 exerts less pressure than static air and a pressure differential is established between the fuel bowl 5 and the fuel ports 21 resulting in a movement of fue-l from the fuel *bowl 5 to and out olf the ports 21, thus charging the passing air with fuel. The quantity of fuel flowing from the ports 21 during the passage of air is all important to the proper and economic operation of the canburetor and the apparatus for detenmining and controlling the fuel flow during different regimes of carburetor operation, is, in large measure, the sub-stance of the present invention.

Functioning to further enrich the incoming air with fuel is an acceleration pump 35. The pump comprises a lcylinder 37 submerged in the fuel reservoir in the fuel bowl 5. Fuel is drawn into the cylinder 37 through an .intake port 38 and upon depression of a reciprocaible piston 39 the fuel is forced into the air passage lil through a ball check valve 41 which is located in the channel 43 communicating with the pump cylinder 37 and the lower portion of the air passage 10. The use and purpose of an acceleration pump is well known yand therefore it will surfce to state that the piston 39 is depressed through the action of a throttle shaft cam 45 whose accelerating rotation (clockwise, referring to FIGURES 3 and 7) forces the ipiston 39 downwardly. The piston 39 is maintained against the lower surface of the cam 45 by the biasing force of a compressed spiral spring 42 underneath the piston in the cylinder 37. The ball check valve spring 41a prevents the ball valve 41 from becoming unseated in the absence of suicient pressure from the piston 39. Such pressure is available only during rapid movement of the throttle shaft cam 45, as in rapid accelerations of the engine with which the carburetor 2 vis combined.

Having described the basic functional features of the carburetor, it will now be explained how the fuel flow is controlled to vary the fuel-air mixture xfor changing conditions of operation of the engine to which the carburetor may be attached.

The fuel metering valve assembly S is located near the bottom of the fuel bowl and projects outwardly of the main carburetor housing 14. The valve assembly 5d includes a hollow cylinder 52 rigidly attached to the exterior side of the fuel .bowl and mounted concentrically with a circula-r aperture '53 in the side wall. The inside of the outer end of the cylinder 52 is threaded to receive a perforated valve casing 54. The open end of the valve casing is slidably inserted into the aperture 53 in the side wall so as to permit free movement of casing 54 when an adjustment is desired in the idling fuel flow, as will be subsequently explained (see FIGURE 8). Disposed for movement in and out of the open end of the Casin-g 54 is a cone shaped needle 55, which penmits fuel to flow between its outer conical surface and the bore in the valve casing, the size of the opening and fuel flow depending on the position of the needle 55 with respect to the opening in the casing. Fuel which passes into the` casing flows through holes 57 in the walls thereof and into a space between the casing and the cylindrical wall 52. From this interspace the fuel passes into the transfer conduit 27 which is tapped into the [cylinder 52 and communicates with the intersp'ace between the cylinder and casing.

In order that the needle 55 may be reciproca'oly movable in and out of the valve casing 54, a needle support block 59 is rigidly secured to the large diameter end o-f the needle and the block is slidably mounted on a pair of parallel 'guide rods 58a and 58h. As best seen in FIG- URE 6, a laterally extending pin 5l) is" threadingly attached to the support block 59 and projects through a slot 75s in the needle control arm 75. Angular rnovement of the control arm 75 about its axis of rotation, presently to be explained, will produce reciprocable movement of the needle 55 and a consequent change in the area of the annular opening between the conical needle 55 and the neck 54o of the valve casing 54. It should be noted that the diameter of the needle 55 at its langest end is greater than the inside diameter of the casing nec-k 54u so that when the support block 59 is allowed to closely approach the casing neck the needle will close the neck, resulting in a complete shut-od of the fuel flow from the fuel 'bowl S.

As previously set forth in this specification, the amount of fuel passed through the ports 21 in the vaporizer bar and injected into the air stream flowing through the air passage 1t! is a function of two variables, the said air ow, and the metering of the fuel by the needle valve 50. In the construction of the present invention both of the variables are independently controllable, the former by a throttle valve in the air passage lil and the latter by the needle valve 50. One of the novel features of the present invention is the co-action of these variables to provide a wide range of fuel-air adjustment for maximum economy and efficiency of operation. The construction of the control mechanisms will now be described.

A rotatable throttle shaft 65 carried in appropriate bearings in the side walls of the air passage l@ extend. inwardly into the fuel bowl 5 and outwardly to the ex tenor of the carburetor body to receive a throttle control arm 66.' in view of the flexibility of the carburetor to provide complete fuel shutoff when the throttle is closed a resilient connection is required between the throttle shaft 65 and the throttle control arm 6e. This requirement will become more fully understood as the description proceeds, however, for the present it will be assumed without further explanation that during the operation of the carburetor when idle fuel flow is the limiting minimum condition (as opposed to fuel shut-olf) the throttle shaft 55 is prevented from assuming the fully closed angular position. The throttle control arm 66 does, however, always return to closed position against stop-screw 67, resulting in relative motion between the throttle shaft 65 and the throttle control arm 66 during the end portion of throttle travel. A very light spring 68 interconnects the shaft 65 and the control arm 66 and has just suflicient strength to make the shaft follow the rotation of the arm. At one end the spring is attached to a bracket 66o, integral with the control arm 66, and its other end connects to the shaft 65 by way of a radially extending pin 65p which emerges from the shaft 65 through a peripheral slot 66S in the collar of the arm 6d which surrounds the shaft 65. Referring to FQURE 1, the shaft 65 is illustrated in the idle setting position (as also shown in FEGURE 3) while the throttle control arm 65 is shown closed Since the shaft 65 is restricted by the greater strength of tension spring 84 from further movement in a clockwise direction the pressure retainer spring 68 is under tension, as shown, during the continued clockwise rotation of the throttle control arm 66. As the throttle control arm e6 is advanced counter-clockwise to an open position the spring 63 will retract and close the gap between the upper end of the slot des and the shaft pin 65p. The gap will be closed completely when the throttle reaches the idle position. Boring all operation between idle and full throttle7 the retainer spring 63 provides suflicient tension between the shaft 65 and the arm 6o to cause the two members to move together as one unit. The length of the slot dos is dimensioned to give rotational adiustment (by stop screw 67) to the fuel cut-ott position of the throttle control arm on without interfere-nce between the shaft pin 65p and the bottom of the slot 66s.

Rotation or the throttle shaft 65 results, among other things, in changing the angle of the air valve plates 70a and lob which, in their horizontal position, substantially close the air passage 2 9. As best seen in FIGURE 6, the air valve plates are constructed of ilat metal strips having a semi-circular midporiion which embraces the top of the throttle shaft 65 and is secured thereto. Angular rotation of the air valve plates a and 75h from their closed position increases the clearance between the ends of the plates and the air passage walls, allowing a greater air flow through the air passage and a consequent gain in engine power output. Rotation of the valve plates 79a and 10b need not exceed 25 degrees from the horizontal position, however if greater opening is found necessary, additional clearance between the plates andthe air intake duct M3 maybe necessary and could be provided by merely altering the shape of the duct, which, by itself forms no part of the invention.

In addition to its function as an operative part of the air valve system, Ithe throttle shaft co-arcts with the fuel metering needle valve 5@ to vary the available fuel flow from the fuel bowl 5 to the ports 21 in the vaporizer bar 25 as a straight line function of throttle position (see FIGURE S). The linkage between the reciprocable needle 55 and the throttle sha-ft 65 is made through the needle control arm 75 which is freely rotatably mounted on the end of the mixture control shaft 80 which is smaller in diameter than the throttle shaft and disposed in an laxial bore therein. The mixture control shaft 80 is held fixed with respect to the throttle shaft 65 and is turnable only through the operation of the mixture control lever 82 attached yto the end of the shaft exterior of the carburetor. Being freely rotatable on the mixture control shaft 80, the needle control arm 75 is free to rotate clockwise (referring to FIGURES 3 and 7) and fully open the needle vlalve 50 in response to the constant lbiasing vforce exerted on the control arm 75 by a tension spring 84 interconnected between the canburetor side wall and the control arm. A finger 65j projecting from the end of the throttle shaft 65 and parallel to the axis thereof acts to limit the opening ,(clockwise, referring to FIGURE 3) rotation off the tates clockwise to open, Ithe needle control arm 75 is allowed to rotate clockwise on its mounting shaft 80 in response to the pull of the tensio-n spring. When the throttle shaft 65 is moved counter-clockwise to close the throttle valves `the projecting finger 65f exertsa force movement on the upper end of ,the recess of the control `arm hub 75h and rotates the needle control anni 75 counter-clockwise Iagainst the retaining force of the tension spring 84.

The carburetor operation, as thus far described, results in a straight line function increase in fuel flow for increases in throttle setting, the fuel flow for any throttle position being sufficient to provide the richest fuel-air mixture ever desired for engine operation. However, it is well known that leaner mixtures are more economical and in certain areas of engine operation are even more desirable from the standpoint of engine performance. It is therefore desirable under some conditions to reduce lthe fuel-'air ratio from maximum rich without reducing the throttle setting (see FIGURE 10). In the preferred embodiment of the present invention, the reduction in fuel flow while maintaining air flow constant is directly accomplished -by rotating the mixture control shaft in a direction opposite to that required to open the throttle (counter-clockwise, referring to FIGURES 3 and 7). Such rotation of the mixture control shaft eiectuates a counter-clockwise rotation of the needle control arm 75 through the co-laction of the T-bar 80T, carried by and normal to the mixture control shaft 80, and a pair of parallel bumper fingers 75x and 75W projecting from the inward face of the needle control arm hub 75h. The position of the said bumper fingers on the hub 75h make possible a movement of the needle control arm 75 to fully open the needle valve 50 Without interference from the Tahar 80T if the mixture control is set at full rich lposition, as shown in FIGURES l and 3. As will be obvious from the figures illustrating the invention, the T-bar may be set at any desired position other than lfull rich, thus acting to limit the clockwise rotation of the needle control arm 75 at some point short of fully opened position las shown in FIGURE 7. Note that in the illustration if FIGURE 7 the throttle shaft 65 is fully open, however, the mixture control is reduced from full rich and the position of t-he T-bar 80T restricts the further rotation of the hu'b 75h. 'I'he restriction of hub rotation limits the further opening movement of the needle 55 Iand a condition exists such as that indicated Ias M2 in FIGURE 9. Condition M3 or M4 `can be achieved, even with full throttle, lby further counter-clockwise (FIGURE 7) r0- tation of the T-bar 80T which will result in further closure of the needle 55.

An idle fuel flo-'w stop 90s is disposed in the path of the needle 'block 59 to prevent the needle from fully closing the neck 54n of 'the casing 54. It is the idle stop 90s which restricts the movement of the throttle control shaft as it is moving in a closing direction, as referred to above in the discussion o-f the pressure retainer spring 68. In some applications, however, it may be desirable to completely shut-off fuel flow when the throttle is closed It is therefore possible in the preferred construction to :lift the idle stop 90s out 0f the path of the needle block 59. A tension spring 92 interconnects the side wall of the carburetor and the idle stop lever 90 and exerts a force movement on the idle stop lever 90 to rotate it about a hinge pin 93 which mounts the lever 90 to the side wall of the carburetor in a recess therein. A deactivator screw 96 is provided to prevent the idle stop lever 90 from being rotated by the force of the ten-sion spring 92 if idle is the desired limiting minimum condition of fuel flow. The deactivator screw 96, when turned 90, is removed from the path of the idle lever permitting it to move, provided that ltlhe mixture control Tahar T is substantially backed off of full rich position. A projection p on the idle stop lever 90 engages the end of the said T-bar to prevent the removal of the idle stop, thus ensuring the continued operation of the engine whenever full rich mixture is provided for, regardless of the position of the throttle or the deactiuator screw 96. Notwithstanding the fact that fuel shut-off operation is selected, it might be highly undesirable to erroneously shut off the :fuel flow by manipulation of the throttle during critical periods of engine operation. Since these periods are almost always accompanied by full rich operation of the carburetor, a safety feature is thus provided. Once the idle stop 90s is raised the mixture control T-'bar 80T must be rotated to full rich position to again lower the stop into engaging position.

OPERATION During operation of the carburetor of the present invention, it is attached to the intake manifold 101 of an engine in any convenient manner slo that the mixture of fuel and air flowing from the `air passage 10 will be drawn into the intake manifold. An air intake duct 103 is secured to the top of the carburetor to provide a source of air to the air passage lll. A source of fuel is connected to the fuel bowl 5 through a threaded connection and a float operated needle valve 112 directs the flow of fuel into the bowl 5, as is well known in the art.

Having already described the mechanical aspects of the operation, reference is made to FIGURES 8 through l0 for a basic graphical analysis of the various modes of operation. FIGURE 8 illustrates the straight line relationship between throttle position and fuel flow, neglecting the venturi effect in the air passage. In FIGURE 8, mixture is assumed to be full rich throughout with parameters of idle adjustment in the fuel metering needle valve 50. Note that with full rich mixture complete fuel cut off is not possible.

FIGURE 9 illustrates the plateau effect on actual fuel flow (again discounting the venturi effect) as a function of reduced mixture control setting and throttle position. Fuel-air ratio is also plotted on the same axis. Note that complete fuel cut off is `possible with a reduced mixture setting, assuming the deactivator screw 96 has been turned.

FIGURE 10 illustrates the effect on fuel-air ratio by reducing the mixture control setting with parameters of throttle setting.

The activation of the throttle lever 66 and mixture setting arm 82 may be made by the operator from a control position by any one of many means known to the art. i

Having thus described the several useful and novel features of the feed mechanism of the present invention in connection wit-h the accompanying drawings, it will be seen that the many worthwhile objectives for which it was designed have been achieved. Although but a few of the several possible embodiments of the invention have been illustrated and described herein, we realize that certain additional modifications may well occur to those skilled in the art Within the broad teaching hereof; hence, it is our intention that the scope of protection afforded hereby shall ibe limited only insofar as said limitations are expressely set forth in the appended claims.

I claim:

1. A variable mixture carburetor comprising;

' a body member forming a fuel bowl and a fuel and air passage adjacent said bowl;

a hollow rotatable throttle shaft traversing said passage and extending into said bowl;

throttle valve means secured to the throttle shaft and located yin the air and fuel passage;

a fuel distributor bar disposed in the passage and having openings therein for the passage therethrough of fuel;

metering means attached to the fuel bowl for regulating t-he quantity of fuel owing to the said bar openings;

conduit means interconnecting said -bar openings and said metering means;

a mixture control shaft disposed in the hollow portion of the said throttle shaft, said mixture control shaft being rotatable relative to the throttle shaft and extending from the end thereof further into the fuel bowl;

control means rotatably mounted on the said extended end of the mixture control shaft. operatively interconnecting the throttle shaft and the metering means; and

means rigidly attached to the end ofthe mixture shaft to provide an operative coupling between the mixture control shaft and the control means, whereby the metering means can be controlled by the throttle shaft and mixture control shaft independently of each other.

2. The carburetor as set forth in claim 1 wherein the control means includes;

a substantially cylindrical hub member having a pair of fingers projecting inwardly into the fuel bowl from an inwardly face of said hub and having a peripheral slot on the rearward face thereof;

and wherein the throttle shaft further includes an inwardly directed finger projecting into the peripheral slot in the hub member and adapted to rotate said hub by engagement with one end of the said slot;

and wherein the means rigidly attached to the end of the mixture shaft comprise a bar forming a T with the mixture control shaft, which bar is disposed between the said pair of fingers and lies in a plane normal to the said pair of fingers.

3. The carburetor of claim 1 wherein the fuel and air passage has a constant cross-sectional area from one end of the passage to the other.

4. The carburetor of claim 1 wherein the metering means comprises;

a housing;

an apertured cylindrical casing disposed within the housing and movable longitudinally with respect thereto;

and l l a conically shaped needle reciprocably movable in said casing, and operatively connected to the control means.

5. The lcombination of claim 4 and fur-ther including stop means positioned in the pat-h of the said needle for limiting the inward travel of the said needle into the casing, thereby creating a limiting minimum fuel flow.

6. The combination of claim 5, and further including a biasing spring interconnecting the said body member and the stop means for removing the stop means from the path of the needle in order that the needle may move :to a position labutting the said casing and thereby yshut off fuel flow.

7. A variable mixture carburetor comprising;

a 'body member forming a fuel bowl and a fuel and air passage;

throttle valve means located in the said passage;

a rotatable throttle shaft extending into the fuel bowl and secured to the throttle valve means;

a mixture control shaft rotatably supported and extending into the fuel bowl;

fuel metering means including a needle valve cornmunicating with the interior of the fuel bowl;

conduit means interconnecting the fuel metering means and said fuelV and air passage;

a biasing member operably interconnecting the said needle valve and the 'body member which tends to fully open the said needle valve;

movable control -means connected to the needle valve and having a hub coaxial with said throttle shaft, said hub having stop means engageaible with the throttle shaft; and

means integral with the mixture control shaft positioned for engagement with the said control means to further limit the opening movement of the needle valve.

References C ed by the Examiner UNITED STATES PATENTS 930,724 8/ 1909 Boore 261-50 1,178,296 4/1916 Cahill. 1,493,227 5/ 1924 Austin 261-50 1,493,894 5/1924 Reece 26141 1,582,594 4/1926 Girin 261-50 2,190,314 2/ 1940 Firth. 2,320,012 5/1943 yRiall 261-50 2,783,033 2/1957 Malik 26d-36 2,856,169 10/ 1958 Mustain 261-51 2,895,723 7/ 1959 Weiland 261--50V XR 3,007,683 11/ 1961 McCracken 261-50 XR HARRY B. THORNTON, Primary Examiner.

HERBERT L, MARTlN, Examiner. 

1. A VARIABLE MIXTURE CARBURETOR COMPRISING; A BODY MEMBER FORMING A FUEL BOWL AND A FUEL AND AIR PASSAGE ADJACENT SAID BOWL; A HOLLOW ROTATABLE THROTTLE SHAFT TRAVERSING SAID PASSAGE AND EXTENDING INTO SAID BOWL; THROTTLE VALVE MEANS SECURED TO THE THROTTLE SHAFT AND LOCATED IN THE AIR AND FUEL PASSAGE; A FUEL DISTRIBUTOR BAR DISPOSED IN THE PASSAGE AND HAVING OPENINGS THEREIN FOR THE PASSAGE THERETHROUGH OF FUEL; METERING MEANS ATTACHED TO THE JUEL BOWL FOR REGULATING THE QUANTITY OF FUEL FLOWING TO THE SAID BAR OPENING; CONDUIT MEANS INTERCONNECTING SAID BAR OPENINGS AND SAID METERING MEANS; A MIXTURE CONTROL SHAFT DISPOSED IN THE HOLLOW PORTION OF THE SAID THROTTLE SHAFT, SAID MIXTURE CONTROL SHAFT BEING ROTATABLE RELATIVE TO THE TROTTLE SHAFT 